IRCC, 70% of black swans are gay. The male couples simply rape a female couple to reproduce.
Nature is funny like that.
I didn't believe you until I looked it up. Whilst you're off with the numbers (it's one in four mated pairs are homosexual males so presumably it's 50% or fewer swans that are gay), that's still pretty amazing.
It adds a whole extra layer to that disturbing scene in The Black Swan with Natalie Portman and Mila Kunis.